Generally, a common light source uses a light emitting diode (LED) to generate a light beam. The illuminating principle of the light emitting diode will be described as follows. When a current is applied to a semiconductor material of Group III-V such as gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs) or indium phosphide (InP), electrons recombine with holes. Consequently, the extra energy is released from a multiple quantum well (MQW) in the form of photons, and the light beam visible to the eyes is generated.
The structure of a conventional LED die will be described as follows. FIG. 1 is a schematic cross-sectional view illustrating the structure of a conventional LED die. As shown in FIG. 1, the conventional LED die 1 has a multi-layered stack structure comprising a substrate 11, a P-type covering layer 12, a multiple quantum well 13, an N-type covering layer 14, a conducting film layer 15 (e.g., an ITO layer), a P-type electrode 16 and an N-type electrode 17. The P-type electrode 16 and the N-type electrode 17 are disposed on the top surface of the LED die 1. The P-type electrode 16 and the N-type electrode 17 are connected with wires according to a wire bonding process, which will be described later. The multiple quantum well 13 is disposed within the multi-layered stack structure. As mentioned above, the light beam of the LED die 1 is outputted from the multiple quantum well 13. Since the light beam is outputted upwardly from the multiple quantum well 13, a portion of the light beam is blocked and lost by the P-type covering layer 12, the conducting film layer 15, the P-type electrode 16 and the N-type electrode 17. Consequently, the overall luminous efficiency of the conventional LED die 1 to output the light beam upwardly is adversely affected. Generally, the overall luminance of the conventional LED die 1 is mainly dependent on the portion of the light beam leaked from the lateral side of the multiple quantum well 13. Consequently, the luminous efficiency of the conventional LED die 1 is not satisfied. In other words, the luminous efficiency of the conventional LED die 1 needs to be further improved.
FIG. 2 is a schematic cross-sectional view illustrating a light source module with the conventional LED die. The light source module 2 comprises a circuit board 21 and plural LED elements 22. The plural LED elements 22 are installed on the circuit board 21. For succinctness, only one LED element 22 is shown in FIG. 2. Each LED element 22 is electrically connected with the circuit board 21 to receive the current from the circuit board 21. Consequently, the LED element 22 emits a light beam. The light source module may be installed within an electronic device (not shown). Consequently, the electronic device has the function of outputting the light beam.
Generally, the light source modules are classified into two types. In the first type light source module, the circuit board 21 has a circuitry for controlling the operation of the LED element 22, and the electronic function of the electronic device to process associated electronic signals is implemented by another circuit board. In the second type light source module, the circuit board 21 has a circuitry for controlling the operation of the LED element 22, and the electronic function of the electronic device to process associated electronic signals is also implemented by the circuit board 21.
In the light source module 2, the LED element 22 is a package structure of a single LED die 1. In addition, the P-type electrode 16 and the N-type electrode 17 of the LED die 1 are connected with corresponding pins 211 of the circuit board 21 through wires 18. Consequently, the LED element 22 can receive the current from the circuit board 21. However, during the process of packaging the LED die 1, the LED die 1 is usually installed on a carrier plate 19. The volume of the carrier plate 19 and the retained height of the wires 18 are the main factors that increase the overall thickness of the package structure of the LED die 1. In other words, it is difficult to reduce the thickness of the light source module with the LED die 1. Of course, the increased thickness of the package structure of the LED die 1 is detrimental to the development of the electronic device toward small size and light weightiness.
With the improvement of technology and living quality, the user's or manufacturer's demands on the functions of the light source module are gradually increased. Basically, the light beam from the light source module provides the illuminating efficacy. In addition, the user or the manufacturer prefers that the light beam from the light source module has more applications. Consequently, some approaches were adopted. In accordance with an approach, an optical structure 23 (e.g., a photomask) is arranged in an optical path of the light beam from the LED element 22 of the conventional light source module. By the optical structure 23, the light beam from the LED element 22 undergoes a secondary optical treatment. For example, the secondary optical treatment includes a light-mixing operation, a light-guiding operation, a diffracting operation, a refracting operation, or the like. In such way, the light beam passing through the optical structure 23 generates a specified optical effect. As mentioned above, the constituents and the package structure of the conventional LED die 1 are detrimental to the miniaturization of the light source module. If the light source module is further equipped with the optical structure 23 to increase the optical effect, it is more difficult to reduce the thickness of the light source module.
Generally, the manufacturer of the light source module and the manufacturer of the LED element 22 are different. Consequently, the manufacturer of the light source module often commissions the manufacturer of the LED element 22 to fabricate the LED element 22 and proposes the required optical specifications. After the manufacturer of the light source module acquires the LED element 22 (i.e., the package structure of the LED die 1) from the manufacturer of the LED element 22, the LED element 22 and the circuit board 21 are combined together through a wire bonding process. Since the LED elements 22 are outsourced, some problems occur. For example, the materials of different LED elements 22 are somewhat different. In addition, the encapsulating materials of packaging the LED elements 22 are somewhat different. Due to the influences of these two factors, there is obvious color difference between different LED elements 22.
In other words, the conventional light source module with the light emitting diode needs to be further improved.